Fluorescence detected circular dichroism (FDCD) will be used to study allosteric transitions in nucleic acids. In particular, the effect of both drugs and proteins on the long range structure of DNA will be investigated. FDCD can provide unique information because it is sensitive to the conformation of a small, defined region in a large macromolecule or complex. One long range goal is to understand the regulation mechanism of certain proteins on gene expression. Additional collaborative work will investigate long range interactions in proteins.